1. Field of the Invention
The invention relates to a device for braking paper sheets, in particular in printing machines.
2. Discussion of the Prior Art
In cross-cutting devices, individual paper sheets are cut out of paper webs and may be flat or else have one or more folds. These individualxe2x80x94collected or uncollectedxe2x80x94products are conveyed by conveyor belts to further processing stations at the usually high machine speed. In order to ensure fault-free further processing, for example on folding tables, the products have first to be stopped or braked.
German Utility Model DE-G 8317604 discloses a braking device in which the braking action can be adjusted manually or automatically. As a result, the machine can be set up for the different requirements of various product thicknesses and lengths. Since, in the case of this device, the sheets are braked at their leading edge, the sheets back up and waves are formed on the individual sheets. During the further processing of these sheets in folding rolls, this leads to creases or other damage.
German reference DE-B 20 00 078 describes a device in which the sheets are conveyed one after another, at a distance, by high-speed lower belts to a braking device which acts on the underside of the trailing edge of the sheets. The sheets are braked by this device and then carried to the stacking point by belts running at the depositing speed. In order to be braked, the sheets are led over a stationary suction chamber which is provided with perforations and which brakes the trailing edge of the sheets by suction by being switched cyclically.
German reference DE-A 26 01 081 describes a braking device in which the trailing edges of the sheets are deflected downward out of the plane of the leading edge of the following sheet by means of an air stream directed counter to the sheet running direction, and are braked in the process. In the case of thin paper grades in particular, and at high machine speeds, it has been shown that the corners of the trailing edges of the sheets turn up during the braking operation and are caught, turned over and creased by the following sheet.
German reference DE-A 43 07 383 shows a braking device arranged underneath the entry plane of the sheets. The device leads an air stream counter to the sheet running direction through a slotted nozzle and over a guide plate. The trailing edges of the sheets are drawn downward and therefore braked by the air stream.
Accordingly, it is an object of the present invention to provide a device for braking paper sheets which is of uncomplicated construction, can be activated simply and which ensures fault-free further processing of the products.
Pursuant to this object, and others which will become apparent hereafter, one aspect of the present inventions resides in a device for braking paper sheets, which acts on the paper sheets, and includes at least one resiliently movable brake shoe, and an electromagnet operatively arranged to input a force on the brake shoe so that the brake shoe acts on the paper sheet.
By a means of the invention, the products can be braked and stopped at the rear, so that they are stretched and rest smoothly on the support, for example a folding table. The device according to the invention has an advantageous compact and simple construction with few components. Additionally, the device can advantageously be activated simply. The invention can be used flexibly, for example as a sheet brake on folding tables, as a brake in retardation stations or upstream of the compartments of paddle wheels, so that the products can advantageously be further processed undamaged.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.